The present study consists of two parts. During one phase of the study, 10 healthy human volunteers will donate a unit of blood, which will be leukoreduced and stored in Additive Solutions-1 (AS-1), and then transfused back to the subjects after 2 days of storage at 4º C in the MGH Blood Bank. The other part of the study consists in the collection of a unit of blood from the same volunteers, but which will be transfused back to the same subject after 40 days of storage. There will be a break of 2 week period in between these 2 study phases. The order of these 2 study parts will be randomized.